Two-Speed PTO Stub Shaft Exchange Improvements

ABSTRACT

A power take-off assembly for a work vehicle including an improved power take-off shaft for installation and removal. The power take off shaft is extended and a cut out section on the first end of the shaft is provided to engage an extended portion of a spring loaded mechanism. Once the cut out section securely fits over the extended portion, the spring loaded mechanism is prevented from axially moving in a rightward direction, thus enabling the spring to hold the gear collar in place to engage the high speed gear. The PTO stub shaft has an extended end with protruding shoulders which serve to capture the snap ring between the stub shaft and the output shaft so that when the stub is moved axially the shoulders will pull the snap ring into the groove on the output shaft which securely fastens the stub shaft. A cut-out section on the front end surface of the output shaft is also provided to allow clearance for the tool to squeeze the snap ring tabs during installation and removal.

FIELD OF THE INVENTION

The present invention relates generally to a reversible two speed PTO Stub Shaft, and more specifically to an improved PTO Stub Shaft for a cheaper and efficient installation process.

BACKGROUND OF THE INVENTION

Power Take-Off Shafts or PTOs are used on agricultural vehicles such as tractors to provide power from the engine to agricultural implements. As the use of PTOs developed over the years, the industry developed a standard for two speed PTOs comprising gear speeds of 1000 and 540 rpms. Thus in order to accommodate industry standards of a particular implement relative to the appropriate gear speed, it is necessary to provide a power take-off assembly which allows quick and easy installation of a proper PTO assemblies, the output shaft has a internally splined portion adapted to axially receive the externally splined reversible power take off shaft to prevent relative rotational movement between the power take-off stub shaft and output shaft. The desired PTO shaft speed is typically determined by the configuration of the PTO shaft end inserted into the output shaft. When reversible PTO shafts are used, as in the case of the present invention, the outer end portion is adapted for engagement with the implement for the selected speed, while the configuration of the inner end portion positions a shifting mechanism against the force of a spring loaded mechanism to selectively engage the proper gear speed.

PTO shafts that are described above are often maintained in place by a locking mechanism, typically a flanged locking mechanism, and arranged externally of the output shaft to which the PTO shaft is coupled. One disadvantage of a PTO shaft and current flanged locking mechanisms is that it tends to be tedious and time consuming to install, which may require the use of an additional person or an additional hand.

Other known PTO shafts are maintained in place by an internal snap ring configured to engage an interior portion of the output shaft. Because of the high force required to compress the snap-ring for installation, special tools such as pliers are usually required to reverse the PTO shaft end. To perform the installation using a snap ring, an operator must push the PTO stub shaft to overcome the high axial force of the spring loaded shifting mechanism (e.g. spring loaded plunger), and at the same time install the snap ring.

It therefore remains desirable to provide an improved PTO stub shaft design that will provide for a quick and secure installation of the PTO stub shaft to the output shaft in a desired orientation without the use of pliers.

SUMMARY OF THE INVENTION

In view of the above, and in accordance with one aspect of the present invention, one object of the invention is to improve the installation and removal process of the two speed reversible PTO stub shaft by enhancing the stub shaft design to enable the operator to easily insert the stub shaft into the output shaft against a spring loaded mechanism by twisting the shaft to align the gear collar teeth to the appropriate gear.

Another object of this invention is to quickly and easily install or remove the power take-off shaft by providing a recess on the front interior top end portion of the output shaft to capture or contain the snap ring which is fastened around the PTO stub shaft. This allows the installer to let go of the tool used to squeeze the snap ring and use both hands to insert the stub shaft against the collar return spring and twist the shaft to align the collar teeth to the gear.

A further object of the invention is to extend the end of the stub shaft and add protruding shoulders in order to further capture or contain a snap ring.

Another object of the invention is to modify the output shaft design by providing a cut out section on the front end surface of the output shaft to allow for snap ring tabs clearance.

Additional objects, advantages, and novel features of the invention will become apparent to those skilled in the art upon examination of the following detailed description of the preferred embodiments of the invention when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a power take-off assembly showing the installation of a reversible power take-off shaft oriented for operation at a speed of 1000 rpm.

FIG. 2 is cross-sectional view of a power take-off assembly showing the installation of the reversible power take-off shaft right before it engages the protruding shoulders.

FIG. 3 is a cross-sectional view of a power take-off assembly showing a fully engaged reversible PTO stub shaft.

FIG. 4 is a cut out view of an output shaft and a stub shaft showing a snap ring securely fastened around its outer surface and a cut out section on the front end surface of the output shaft.

DESCRIPTION OF THE PREFERRED EMBODIMENT

While the present invention is susceptible of embodiments in various forms, there is shown in the drawings and will hereinafter be described a preferred embodiment of the invention with the understanding that the present disclosure is to be considered as setting forth an exemplification of the invention which is not intended to limit the invention to the specific embodiment illustrated.

Referring now to the drawings, wherein like reference numerals refer to like parts throughout the several views, there is shown in FIG. 1 a power take-off assembly 10. The power take-off output shaft 20 carries a gear collar 14 which is splined onto the PTO output shaft 20 so that limited axial movement is permitted. The gear collar 14 located between gears 16 and 18 and depending on which particular speed is desired by the work vehicle operator is capable of sliding axially between a high gear speed 18 and a low gear speed 16, respectively 1000 rpm and 540 rpm.

FIGS. 1-3 show a snap ring 24 fastened around the outer surface of the stub shaft 12 wherein the snap ring 24 seats within a groove or recess portion 28 along the front interior bottom surface 40 of the PTO output shaft 20. Once the snap ring 24 is aligned and seated within the recess 28, the snap ring becomes locked within the recess and axial movement of the PTO stub shaft is limited.

The operation of the foregoing preferred embodiment of the invention will now be described with reference to FIGS. 1 and 3. In FIG. 1, the PTO stub shaft 12 having a preferred extended end of 9 mm, is shown at an initial installation point wherein the PTO stub shaft 12 is moved axially until the PTO stub shaft 12 locks into the interior splined top end portion 38 of the front interior surface on the output shaft 20. The snap ring 24 fastened around the outer surface of the PTO stub shaft 12 is simultaneously seated within the recess 28 on the front interior bottom surface 40 of the output shaft. The interior splined top end portion 38 of the output shaft prevents the PTO stub shaft 12 from moving axially or in a rightward axial direction while the groove or recess 28 located on the front interior bottom surface 40 of the output shaft 20 prevents the snap ring 24 and the PTO stub shaft 12 from moving axially or in a leftward axial direction. This improved process enables the work vehicle operator or installer to use both hands on the PTO stub shaft 12 to overcome the high force of the spring 26 during installation and force the gear collar 14 proximally or rightward to engage the low gear speed as shown in FIG. 3 to condition the output shaft 20 and the PTO stub shaft 12 for low gear speed operation. As previously mentioned, the PTO stub shaft 12 has a preferred extended end of at least 9 mm for better gripping during installation and removal, however, the PTO stub shaft 12 may be extended anywhere between 9 to 20 mm to achieve a similar desired result. The length of the PTO stub shaft 12 is determined by how much gripping area is desired by the operator to ease the PTO stub shaft installation and removal process.

In FIG. 2, the PTO stub shaft 12 is shown at an installation point right before the snap ring 24 engages the protruding shoulder 30 of the PTO stub shaft 12. The protruding shoulder 30 is attached near the center of the PTO stub shaft 12 between the first 32 and second ends 34 and act as a means for limiting the snap ring 24 from moving axially. Further shown in FIG. 2, the PTO stub shaft 12 is moved closer to the recess portion 28 on the interior bottom surface of the PTO output shaft 20 and the snap ring 24 once aligned will seat itself within the recess 28 of the output shaft 20, thereby locking the snap ring 24 and PTO stub shaft 12 in place to prevent axial movement of the PTO stub shaft 12. The recess 28, the interior splined top end portion on the front interior surface 38, and the snap ring 24 captured by the protruding shoulder 30 may be a means for limiting axial movement of the PTO stub shaft 12. FIG. 2 shows the PTO stub shaft 12 engaged with the spring loaded mechanism 22 and this engagement exerts force against the PTO stub shaft 12 in a leftward direction.

FIG. 3 shows the PTO stub shaft 12 in a locked installation position and oriented at 540 rpms. In this locked installation position 28 the PTO stub shaft 12 is firmly seated within the recess portion 28 and the interior splined top end 38 of the output shaft. In this position, the spring loaded mechanism 22 is fully engaged by the PTO stub shaft 12 and the force of the spring 26 is fully exerted in a leftward axial direction. Once this force is exerted, the interior splined top end portion 38 and the recess portion 28 on the output shaft 20 both operate to capture the PTO stub shaft and prevent the PTO stub shaft 12 from moving either in a leftward or rightward direction.

(not shown) If it is desired to change the gear speed by reversing the PTO stub shaft 12, the first end 32 is inserted into the output shaft 20 while the second end 34 is oriented towards the work vehicle. The operator will then compress the snap ring 24 using a tool similar to pliers, and the stub shaft 12 will be removed. When the stub shaft 12 is removed, the spring 26 continues to force the gear collar 14 in a distal or leftward axial direction in the illustrated embodiment, until the gear collar 14 is moved activating the low gear speed.

FIG. 4 illustrates a front view of the PTO stub shaft 12 and a snap ring with tabs 24 fastened on the outer surface of the stub shaft. The front end surface of the output shaft 20 is provided with a cut out section 36 to allow for clearance of the snap ring tabs 24 as the PTO stub shaft 12 is installed.

From the foregoing, it will be observed that numerous modifications and variations can be affected without departing from the true spirit and scope of the novel concept of the present invention. It will be appreciated that the present disclosure is intended as an exemplification of the invention, and is not intended to limit the invention to the specific embodiment illustrated. The disclosure is intended to cover by appended claims all such modifications as fall within the scope of the claims. 

1. An improved power take off assembly system for installing and removing a two-speed power take off on a work vehicle comprising: a PTO output shaft having a front interior bottom surface, a front end surface with a cutout section, a front interior surface having an interior splined top end portion, and a rear end; an externally splined reversible PTO stub shaft engageable with and secured by the interior splined top end portion and having an extended end, a center and a protruding shoulder attached near the center; a snap ring captured by the protruding shoulder and fastened around the PTO stub shaft; a gear collar fixedly mounted on the rear end of the PTO output shaft and axially movable between a high gear speed position and a low gear speed position; a spring loaded mechanism coupled to the gear collar acting as a distal stop to prevent axial movement of the PTO stub shaft.
 2. The improved power take off assembly system of claim 1 wherein the protruding shoulder prevents the snap ring and PTO stub shaft from moving axially and engaging the spring loaded mechanism.
 3. The improved power take off assembly system of claim 1 wherein the front interior bottom surface of the PTO output shaft has a recess for securely seating the snap ring.
 4. The improved power take off assembly of claim 3 wherein the seating of the snap ring within the recess prevents the PTO stub shaft from moving axially and engaging the spring loaded mechanism.
 5. The improved power take-off assembly of claim 1 wherein the snap ring has a pair of tabs.
 6. The improved power take off assembly of claim 5 wherein the cut out section provides clearance for the snap ring tabs during installation and removal.
 7. The improved power take off assembly of claim 5 wherein the snap ring tabs provide space to squeeze the snap ring during installation and removal when using a pair of work tools.
 8. The improved power take off assembly of claim 5 wherein the snap ring tabs are bent out radially to butt against the PTO stub shaft.
 9. The improved power-take off assembly of claim 1 wherein the interior splined top end portion on the front interior surface prevents relative rotational movement between the PTO output shaft and the externally splined reversible PTO stub shaft.
 10. The improved power take off assembly of claim 1 wherein the interior splined top end portion on the front interior surface limits the externally splined reversible PTO stub shaft from moving axially.
 11. An improved power take off assembly system for installing and removing a two-speed power take off on a work vehicle comprising: a PTO output shaft having a front interior bottom surface, a front end surface with a cutout section, a front interior surface having an interior splined top end portion, and a rear end; an externally splined reversible PTO stub shaft engageable with the interior splined top end portion and the front interior bottom surface, and having an extended end, a center and a protruding shoulder attached near the center; a gear collar fixedly mounted on the rear end of the PTO output shaft and axially movable between a high gear speed position and a low gear speed position; a spring loaded mechanism coupled to the gear collar acting acts as a distal stop to prevent axial movement of the PTO stub shaft; a means for limiting axial movement of the externally splined reversible PTO stub shaft.
 12. The improved power take off shaft of claim 11 wherein the limiting means is a snap ring captured by the protruding shoulder on the externally splined reversible PTO stub shaft.
 13. The improved power take off shaft of claim 11 wherein the limiting means is the interior splined top end portion on the front interior surface of the PTO output shaft.
 14. The improved power take-off shaft of claim 11 wherein the limiting means is a recess on the front interior bottom surface of the PTO output shaft.
 15. The improved power take-off shaft of claim 11 wherein the limiting means prevents the PTO stub shaft end from engaging the spring loaded mechanism. 